Yes, as long as all the supporting documents are submitted and the background checks are completed, your passport may be stamped as proof of permanent residency for travel, work, etc. The actual laminated permanent resident card
(Green Card) will be issued separately later, however, your permanent resident status starts as of the original approval date.
Yes, marriage to U.S. citizen based Green Cards are temporary in nature. The United States Citizenship and Immigration Services (USCIS) grants Conditional Permanent Residency for two years, after which you need to file for Removal of Conditions to get a permanent Green Card. The USCIS does a second check on the marriage after two years because marriage is a relatively easy route to get permanent residency in the U.S.
Note: If you have already been married for two years when you apply for a marriage to U.S. citizen based Green Card the USCIS will grant you a permanent Green Card.