Add new frame, delete existing frame and rearrange frame an animated GIF file

Question

Is there a windows application that can add a new frame, delete existing frame(s) and rearrange existing frames from an animated GIF file?

The application needs to:

• Freeware or Open source (no watermark after add or delete or rearrange frames)
• Portable ('good to have')
• Offline (do not require Internet in order to function)
• Support big animated GIF file (should not freeze or crash when opening a Animated GIF file of minimum size of 1 MB to a max size of 500 MB given that the hardware free RAM is more than 2GB and a i3 CPU is used.)

I tried GifCam but it can only allow delete. It does not allow to add a new frame at any position or rearrange existing frames.

I also tried PhotoScape but it crash when opening a animated GIF of 1 MB.