If the bolts are rusty, wipe them with kerosene to make it easier to unscrew; Carefully remove the toilet fasteners. Most likely, these will be anchors or dowels; Disconnect the drain from the sewer pipe. In Soviet-built houses, the drain is cemented. https://www.trngamers.co.uk/post/34318_https-msnho-com-blog-what-determines-reliability-and-durability-new-toilet-https.html