Ladies and Gentleman: One question: can I use MCP5500 as a remote for Beogram CD5500 directly, or I need a Beomaster?

I already own too many equipments: SCD-1, SCD-XA5400ES, JVC 1050, Revox 126, Revox 226-S, Revox 750-II, Revox 760, Quaad FM4 x 2, 34 x 4, 405 I/II x ?, 306 x 3, 606-I/II, 909. B&O Beomaster 2400 (most of them need to be repaired, especially Revox except the tuner: brand new!), and one more Beomaster 5500 just for remote control sounds a bit too much.

You need the Beomaster.  It's the 'brain', and controls the other components.

Do I simply connect the 7-pin DIN from Beomaster to Beogram CD? And my CD RCA can be connect to somethingelse?

The CD 5500 should be hard-wired with the 7-Pin DIN cable that plugs into the Beomaster.   Yes, you could connect something else into the CD RCA inputs on the Beomaster.

I believe some CD5500s just have a 7 pin DIN socket rather than the captive lead. Just attach this to the Beomaster via a 7 pin DIN lead. The RCA sockets are there to allow you to attach it to other makes of amplifier though the lack of remote makes this less than useful. There is also a digital out which means that you can use it with Beolab 5s!