Answers:（1）我住在351号楼（2）我住在23号楼。Tips: (1) We normally use arabic number rather than hanzi number in writing, unless in very official circumstances (2) The addition of “在” makes the sentences more natural, although people will still understand you without it : )

1 and 2 are both correct, but 1 is better. For 4 and 5, only 5 is correct. Because if the number is less than 100, we can only say 二十三 for example. But if more than 100, we can say both 三一五 or 三百一十五。

2和5是正确的

I would pick 1 over 2, and 5 over 4. When the number 1 is used in ordinal number (as seen in example 1), "1" is pronounced as "yao" instead of "yi" for clarity.