Is there a way to copy amiga files saved from the internet in Linux RH or Windows 9x/XP to an Amiga 880K floppy?
No, not without special hardware.
I could copy the file to a 720k DOS disk and then use an emulation on the amiga1200 to get the file (I guess).
Yes, see below.
Also, I was thinking I could copy the file to a disk in linux if I could get Linux to format it to 880K.
No. You can't without special hardware.
Does the 1200 come with a 1.44m Floppy?
No, not standard.
can it read 1.44m floppies?
No.
Can Linux format a disk in 880k
Not in amiga track format, no, unless if you use
special hardware. This is a floppy controller problem, not drive or software problem.
and is there program that will read a 720k DOS disk in WB?
Yes. Storage-floppy has the PC0 mount entry.
Insert Storage-floppy into floppy drive, open DOSDrivers -drawer and doubleclick PC0-icon. Insert Workbench floppy back as requested. The internal floppy drive will now read/write 720K MSDOS formatted disks. If you want this as a permanent feature, drag&drop the PC0 icon into Workbench-floppy Devs/DOSDrivers -drawer.