Can't help with 1. Has been a while since I messed with GG and it's palettes.
For 2, GIF only supports 256 color palettes so you can't use more than 256 colors per frame. It shouldn't alter the colors, though; if it does, it's GG's fault. GIF palettes store colors with one byte per color channel (R, G, B), if I'm not mistaken, so True Color colors shouldn't be a problem at all (as long as you don't use more than 256 different ones in one frame).
Oh hey I'm back to bring you this: TFR_PALETTE.pal! (Right-Click and Save)
On the palette window in GG, click the downward-pointing arrow directly below the color grid. Choose "Load Palette..." from the popup menu. "Import from File...", choose this .pal file here, select all colors from the loaded one on the left, click the upper-left one on the right grid, "OK" and you should be set with the official TFR palette.
I took the colors from the palette on one of the images in the first post in the official TFR topic.
For 2, GIF only supports 256 color palettes so you can't use more than 256 colors per frame. It shouldn't alter the colors, though; if it does, it's GG's fault. GIF palettes store colors with one byte per color channel (R, G, B), if I'm not mistaken, so True Color colors shouldn't be a problem at all (as long as you don't use more than 256 different ones in one frame).
Oh hey I'm back to bring you this: TFR_PALETTE.pal! (Right-Click and Save)
On the palette window in GG, click the downward-pointing arrow directly below the color grid. Choose "Load Palette..." from the popup menu. "Import from File...", choose this .pal file here, select all colors from the loaded one on the left, click the upper-left one on the right grid, "OK" and you should be set with the official TFR palette.
I took the colors from the palette on one of the images in the first post in the official TFR topic.