w10 upgrade, if followed correctly, should be relatively seamless. about forced upgrade, know that we all have different hardware and software in our systems. some are fine if you do it, but some are bad. that's why forced upgrade is never recommended, because when you do that you just increase the potential risks to fail. however if you know what you're doing and prepare for the worst, nothing bad will happen even if the upgrade failed. no matter what you do, make a full backup of your system and data before upgrade.

whether to upgrade or not, it's really up to you. you might wanna take the time to read about w10. there are features that some users find them hard to swallow and eventually revert to original os. (read previous posts for details and comments)

the free upgrade offer starts with upgrading an activated os when it's connected to the internet. the whole process will not ask you for key. once you have confirmed the new os is activated online, you can proceed with a clean install. just skip to next when you're asked for a key.

a direct clean install of w10 will not get activated with old key.

about drivers, it's best to look for compatible drivers (as complete as possible), download them before upgrade, just in case. usually you can find the latest drivers from manufacturers' websites.
yes i do that. i'm fine with the current boot time. if you must have fast boot, then don't.
what's the brand of your laptop? a factory reset from stock factory image usually will activate automatically. if it doesn't work, try phone activation. at administrative command prompt type slui 4 and follow the instructions.

besides ccleaner, you can also try wise regcleaner, https://forum.lowyat.net/topic/909723 run reg cleanup and system tuneup.

it's up to you. check out the posts here for ideas.
right. if you do not know what it does to your os, using these system tweaking software that involve windows registry is potentially unsafe. everything is done at your own risks. however talking about breaking things, how many times do we screw the os up just by using reg cleaners? the popularity of the tools may prove otherwise.

these days, reg cleaners are kind of user-friendly. they always create backups before committing changes. so if you're unsure, do not turn that backup function off. now what if i screwed up the os really big time? i just restore it from reg backups. if the damage is so beyond repairs, i just restore the os from a working system image, or do a reset, or a clean install.

the thing is, ms ships their os with default settings, but there is no such things as 'one size fits all'. in order to make a system run better, it's up to users to remove what are useless to it, and tweak the rest based on requirements.

of course ms will not support and is against the use. they have all the things they can say, i.e. when they provided their own tools to this, and when they decided to discontinue them.
what Cynox said.

why when i want to upgrade my wins 7 to wins 10 it appears this message
http://postimg.org/image/8kscdb0p9/
i have done all the steps to rectify this error on windows website but still this error happen