Harry Rhodan

It means at least one of your mods is incompatible with the version of the game you're running.

If you still want Steam to update and launch the game you can also just follow these general instructions:
https://www.howtogeek.com/269515/how-to-move-a-steam-game-to-another-drive-without-re-downloading-it/

The launcher has been abandoned since version 1.0. You need to download the most recent version from the store you bought it from.

You're running out of memory because you are launching the 32bit version of the game and not the 64bit version.

You log is full of audio errors because the game has some problem with your sound driver. Older threads suggest that reinstalling your sound driver or using the generic windows driver should do the trick.

You put mods into the gamedata folder, not the Squad folder. You should never ever put anything into the Squad folder.
And please use punctuation.

Your payload is too long and light, your CoM way too far down. Never use the CoL indicator for rockets. It is telling you where the lift of the wings and winglets will be and not where aerodynamic pressure attacks.

No. They would still detach into four separate parts. In this game you can branch parts from a common root part but you cannot merge the branches back together. In your case you branched off four separate engine parts and used struts like duct tape to tape them together. But you would need to actually use structural parts like girders and the like to connect them, which you can't because you can't merge branched parts in the VAB.
Your skycrane can only have one attachment point to your rover. You need to attach those four separate engine things to a common root part and then attach that root part to your rover. If you absolutely need multiple attachment points you'd have to manually attach them in orbit with a Kerbal using the KAS winches.

Where's the problem? There's a pretty obvious delete button on the screen where you have to select your saves. And if you already know where your install folder is then you can go to the saves folder and delete them manually.

The usual answer: Use the 64bit executable and not the 32bit one.

Look at the pitch indicator on the first screenshot. It's not in a neutral position. I don't know if it is SAS fighting to keep it stable, but it might be that you either set trim to constantly pitch up (reset with Mod (Alt on Windows) + x) or that you might have a joystick or controller attached that's not exactly calibrated.

You simply can't. They only offer the last stable major releases but not the point releases. That's why you should make backups of your game files or should even play from a separate copy of the game that Steam won't touch.

As far as I know the new update finally killed the compatibility with the GMA 950 family.

Yes.

In my experience decoupling animations in the VAB are usually a sign of a broken mod.

You are still using the 32bit version and ran out of memory.