Don't roll questions on different topics into the same posting. Ask them as separate questions. If somebody knows the answer to one question, they might be put off submitting the answer by the other questions.
1-What are the difficulties [when buying online]? How is Amazon etc? - I don't have any difficulties as long as you follow the instructions. Make sure the site is using HTTPS and you have the green padlock symbol by the address bar.
2-Why do some printers have wifi? - Because the manufacturers have added WiFi as an alternative to using Ethernet or USB.
3-What can i do if the boot is working and not windows? Any program? - If no operating system will load, then boot is NOT working. Create an installation medium and boot from that then try running the repair tool if there is one. This sort of problem is normally caused by carelessly deleting system files or accidentally dragging folders into other folders.
4-Why is Chrome closing without reason in the tablet? - There will be a reason. I assume you mean the Chrome browser and not the Chrome operating system. Try uninstalling Chrome and reinstalling it. If that doesn't fix it, there may be a bug or corruption in the tablet's operating system or a hardware fault.
5- If a modem's drive works in Windows 7 will it work in the Windows 10? You would not normally have a modem drive[r] unless you are connecting to a USB modem. Normally with Ethernet, it is simply using the operating system's normal Ethernet driver. For WiFi, that does not come from a modem, it comes from a router and again there is no modem driver. You might need a wireless adapter driver, and that can be specific both to the particular adapter and the particular version of Windows.
6-How is write the Windows key in the label under the notebook? How to write it in the Microsoft site? Capital letters? - Not sure what you are asking.
7-Why do the link here have many numbers and letters? How to find an old question if we asked a lot? - Click on your account name or icon and look at the list of questions. This probably won't help is you are too shy and always ask anonymous questions or submit anonymous answers. Since your displayed name is only a nick name you have chosen to use, it seems pointless to ask anonymous questions unless you are a troll.
8-If the Tv is without color is it to fix by the TNT adaptor or by the TV? - Contact the TV installer or service supplier and get them to sort it out. It could be either the adapter or the TV or you might just be viewing monochrome programs or have the colour saturation level set to zero.