I would take it back apart and make sure you have the battery connected properly. An iphone will flash an apple logo then reboot endlessly with no battery present. The watch probably does the same. If the battery is installed correctly then you may have a bad battery. The battery on the series 1 watch can be a little tricky to get it plugged in all the way.
Make sure the glass and frame are completely clean and then use tesa tape https://www.mobilesentrix.com/tempered-glass/liquid-tempered-glass/tesa-tape Other people swear by 3m primer 94 3M Primer 94 Pen 0.2oz | Vinyl Car Wrap Application Tool (5 Pack) https://www.amazon.com/dp/B00HVEW9ZW/ref...
i dont think anyone sells it with the home button included because your supposed to transfer the home button to keep touch id. if you do need a new home button you must purchase it separately. https://www.mobilesentrix.com/replacemen...-parts/apple/ipad-parts/ipad-5-2017
That is very common with a defective screen I would change the screen and see if it works if not it could be a board issue and if you find a reputable repair shop that can get the schematics and parts for it they should be able to fix it
The best way to find out is to open it and see but be very careful. The screen is glued on you need heat and a thin plastic card and alcohol to open. Also if you haven't done this type of work before then I would leave this to a professional. Someone that has a history of working on imacs
https://www.mobilesentrix.com/replacemen...-parts/samsung/galaxy-s-series/samsung-galaxy-s7-edge Make sure you get one with the frame. It's the best way. Also if you dont already have a background in replacing screen then you should leave this job to a professional.