Is there a support for ATTiny87?

Other Hardware 3rd Party Boards
1

20 pin IC, 15 usable I/O pins with 2 VCC, 2 GND, and a reset pin. Slightly more than ATTiny84 (14 pin package, 11 usable I/O) and smaller than ATMegaxx8 (28 pin package, 22 I/O if not using external clock)

ATtiny is about 50 cents cheaper than ATMega328 on Digikey FWIW.

2

Sure, using TinyCore.

3

Sure is. GitHub - SpenceKonde/ATTinyCore: Arduino core for ATtiny 1634, 828, x313, x4, x41, x5, x61, x7 and x8

That said, unless you need that LIN/UART module, an 861 or 1634 are probably more appealing attiny's.