please suggest a free good video editing tool preferably online web based app or if there's none then PC software also would be ok. The app must be able to get the video from youtube video url and i can trim important parts of the video and rejoin them to make a shorter gist video for my study. Also i should be able to download the output video
I know a very good free video editing tool & a very good free YouTube downloader, but I think you're expecting too much to have them in one tool.
Basically one is a highly professional video suite, the other is a very dubious way to steal from YouTube. They're very different markets.
By far the best free video editor is DaVinci Resolve [Mac/Win/Nix.] It is a full-loaded professional suite. It also has a steep learning curve & a 3,600-page manual. You only need the paid version if you are a professional studio with hardware vision mixers etc to integrate.
The best way to steal videos for free from YouTube is using JDownloader. If you use its browser plugin, it can pick up any copied url. For YouTube it presents all the available video & audio versions, so you can choose which to download.
May recommend FlexClip Video Editor Business video editing tool. Apart from the basic video editing features like trim, zoom, rotate, split video, change video resolution, change video speed, add logo to video, add watermark and many many others it CAN create video from photo, has voice recorder... All these greate features are included into a free version of flexclip which has some limitations such as watermarks at the output video but the great thing is that the company runs giveaways from time to time. I have found flexclip video editor business giveaway you may try to use.