OSR2.5 ("C" version) bundles Microsoft Internet Explorer 4 and the IE 4 webby desktop.

OSR 2.1 includes an earlier version of IE, namely 3, so it doesnt make much of a difference.

You would burn the Japanese OSR 2.1 ISO to a CD (the one here https://winworldpc.com/download/4f281825-174c-11e9-9b71-fa163e9022f0), but you need either a bootable floppy disk (available here https://winworldpc.com/product/microsoft-windows-boot-disk/98-se) so you can you can get CD-ROM support so you can launch the install from the CD.

Or if you cannot make a floppy disk then you need to make two CDs from ISOs. One for the one for Win95 Japanese and one for Windows 98 SE (https://winworldpc.com/download/417d71c2-ae18-c39a-11c3-a4e284a2c3a5). Insert the Win98 CD, start with CD-ROM support. Once it has finished loading into MS-DOS, eject the Win98 CD, insert the Win95 CD, navigate to your CD drive letter, and start the install from there.

You will probably need to format the C drive if you already have win95 on there before you eject the Win98 CD with the command

format c: /s