No, not yet
2001 - the first 2 digits are the year of manufacture.
See page 18 of the manual, available at the following link. http://www.eaacorp.com/Manuals/mp153.PDF
Yes, some of the remington tubes will but not all. I have a remington modified choke in my mp 153 right now.
On the Baikal/Remington SPR 310 O/U, you simply push the trigger forward to select the top barrel, leave it alone to have the bottom barrel fire first.
Cleaning instructions start on page 20 of the owners manual which is available at the following link. http://www.eaacorp.com/Manuals/mp153.PDF
Parts for these shotguns are hard to find. EAA Corp carries parts for Baikal shotguns. A good gunsmith might also be able to help make some parts.
Remington Arms bought out Baikal firearms. A new Baikal model MP153 12 gauge shotgun can be purchased for $489.99 at Southern Trading Company and Pawn located in Bainbridge, Georgia (Contact Edwin McCullers at 229-248-0024).