yes you can by link

Yes you can, definitely. Just upload the video on YouTube as normal process.

Yes, just record the video on the device of your choice and then upload that same video to both your TikTok and YouTube accounts.

If you are wanting to add existing TikTok videos to your YouTube account and you no longer have the original video on your device you might try a platform like repurpose.io.

There is a way to download/save TikTok videos to your device and then upload it to YouTube. However, it will have the TikTok logo. I would recommend you upload the video to YouTube separately and also take advantage of other social media platforms such as Instagram.