Yes, a short beta can help you to promote your channel for free. Its views are not counted for monetization but subscribers count. So work smart, because short beta can help to viral your channel.
Not really need to ask for it because very few people will allow you to do it. All roasters just roast them, not rely on permission, etc. But you have to try to keep roasting to a limit and strictly avoid using religion or any sensitive topic.
For making attractive YouTube video thumbnails the graphics and design of thumbnails should be high and professional. Use the interesting text on the thumbnail to grab the attention of the viewers but never used the misleading titles on the thumbnail. Canva and photoshop tools are perfect to create excellent thumbnails.
All YouTubers use different editing software because it depends on the niche, editing type, and budget. If you are a beginner and don't need a highly advanced level editing software then shotcut, iMovie, davnice softwares are perfect for you. In case, you want to use mostly used and reliable paid editing software then Adobe Premiere Pro and Final Cut Pro are on the recommended list.
Regular analysis of your YouTube channel is an important factor in maintaining and growing your YouTube channel. Therefore, to check the video ranking on YouTube various tools are available in the online market but my recommended tool is tubebuddy extension. It has multiple benefits for you at no charge. With this extension, you can check the ranking of your YouTube video on particular tags easily and free as well as the option to search keywords, tags, and many more.