Any advice or hints, for beating the "Challenges" Game mode?

Like what character to use, if there is some trick etc.? I lack only 7 challenges, i have done EVERYTHING to this game there is to be done (excluding mods, lol)!

I can't do the 2 challenges on the elevator, 1 to always drop them down and 1 to drop no one, the falling barrels, the bike challenge, the robot arm, the protect blaze (this even has damage from the player done to blaze accidentally) and one else i don't remember which...

I would appreciate any help!

Personally I recommend X for the elevator challenge in which you throw them off the pit, or elle if your goal is to keep the out of the pit (stand up in the far-right corner and they can't knock you off).

The bike challenge is tricky - basically you just have to memorize it; I recommend using the accelerate ability rather than the wheelie for most enemies; when you run into enemies organized in to rows upward and downward, it's best to pop a wheelie and dash through them.

For the protect Blaze challenge, just try to knock the pipes out of the enemies; hands early on, and then be light on your feet and try to distract them away from Blaze.

The Dr. Dahm claw challenge just requires good timing.

I have completed all challenges several times in the past, and the bike and elevator ones have given me no end of grief then. Some others also took me tons of retries.

Since this is a new save, and on 5.1, I've had to redo them. Yesterday I did half of them, but now I am at the point where I have to face the same tough ones you have to deal with.

To see if I could help you out here, I did just finish the "Protect Blaze" event, on my 4th and 7th tries. I can't seem to prevent her getting smacked by the left Donovan right away, unless I do it FOR HIM. Axel3 hits a lot less hard bare knuckled (see what I did there?) than a Donny3 carrying a lead pipe. Also, if you manage to get Blaze to land at either side of the screen, you can much more easily draw the enemies away. Against the pistol enemies, just kick them offscreen. If they come at you from both sides, do a running jump kick to knock them away then make use of their long recovery time to run to the other side of the screen and knock the other one(s) offscreen. If they take aim at Blaze, well, play bodyguard and eat the bullet.

Elevator events: X is great for both. Quick shoulder throw (so less chance to kill other enemies accidentally) and offensive vault (low damage and lets you get out of a grab without double vaulting) shine here. Besides, you can mow down the whole group with fairly low damage from defensive special or target single enemies with pinpoint accuracy using the offensive special. And he's fast. And he has amazing jump attacks and blitzes. Did you know X's neutral jump attack blocks projectiles like throwing stars? (Well, it used to in 5.0a and why would they remove that?!)

Well, finished the rest of them except the bike stage today.

In the event where you have to prevent the bottle from breaking, using Max and his Blitz-1 worked on the first attempt for me. Same for the "beat 2 Shivas" challenge. Cheap? Maybe. Effective? Hell yeah.

The "don't kick enemies off the platform" challenge was 10x harder than the opposite; mr.X was used for both. For the one where you have to prevent them from falling off, I tried many characters; I got furthest with Rudra and Shiva a few times, Zan definitely did OK as well since he has a lot of control over his throw directions (forward, backward, slamming) and can do Z-axis sweeps with his Blitz2/3 and spam shield dash. He also does great with the pipes and knives you get in the challenge. Skate2 does OK too for the same reasons; in addition, his throws tend to have a fairly short distance. But he's tricky.
Adam and Axel1... NO. Just no. Their defensive specials knock enemies really far away. And Adam is especially hard to use here since you could unintentionally kick an enemy into a group of others with your basic combo finisher.

Mr. X is where it's at for me, try it. When the enemies with the pipes show up, or when the Soozies set up themselves across from you for a jumping kick, move to the top right corner of the elevator and use the defensive special to spray hot lead across the screen. Just make sure you aim it to the left 'cause it could easily knock enemies (especially airborne ones) into the pit.

TIP: slightly to the left of the safe spot (top right, where you can't be knocked off by enemies) at the very bottom right edge of the elevator platform, is where enemies sometimes like to stand. Especially knife galsia, who in between stabbing runs can get stuck facing AWAY from you if you stand at the top right. When he does that, don't machinegun him; if you hit an enemy facing away from you with the bullets, they will fall TOWARDS you and the edge of the screen.

Make sure you keep moving around. Non-offensive running jumps are good, they prevent enemies from mobbing and comboing you. Running jump with down+attack into shoulder throw works very effectively but you have to be precise with it. If you do an accidental back throw it's probably over. And when you are facing the left, don't do shoulder throws (duh), try vaulting so mr.X does his kick which gives you tons more control over where enemies fly.

In general, whenever there's multiple enemies onscreen and you have full special gauge, spray some defensive bullets to the left to keep them away from you and the bottomless pit.
Then play opportunistically:
-run diagonally and go for quick grab into shoulder throw/vault kick, or just use blitz-0;
-roll to avoid Soozies/Electra;
-jump (without attacking) over groups that are hanging out in the top right part of the screen.
Use these tactics to manage the enemies on the screen until the gauge has (mostly) recharged and then do the defensive special from top right corner again.

Priority machinegun targets are:
-Donny3 with pipe (try to throw it away immediately when it is dropped);
-SoR3 Phoenixes (the blocking kickboxers who come at the very finish when you are low on life);
-Soozies/Electras (as they will sometimes accidentally jump offscreen diagonally... only really see this when I use Max for these challenges for some reason...).

Dahm bombs:

Adam's pretty useful for some challenges it turns out.

Adam:

Rudra:

Bike stage? Great advice has been given already. Good luck and good hunting.