As far as I know, you can put whatever you want. Now, you should? If you think this gift will make this person a little happier and you want to gift it, well, yes
https://forum.scrap.tf/support go here.
You may need to post the screenshot of the error + you in the queue showing the bot's name + your trade URL
Everything I said in the support ticket (the link I posted)
Please, next time if you have a problem with the bots, go here:
https://forum.scrap.tf/support (and yes, go here now)
You have to send them the screenshots of the error and you being in the queue, also the link to the auction and your trade URL
As far as I know, there are 2 ways here in scrap:
You win it in a raffle (very unlikely because almost noone raffle it away, and if they do, a lot of people would join so everyone would have a very low chance)
Someone with an extra Upgrade to Premium and generous enough gift it to you
I think not. The colored part is the damage, not its health. Sometimes I noticed the colored bar going back just a pixel or two, but I'm sure that's because there are a lot of people damaging it that not every user are "synchronized"