I own 100% LLC -BB owns 50% of LLC -BF01BF01 owns a lot to be sold in 2023.If BF01 has expenses, can they be recognized when the lot sells?Do I file Sch C for B?

If you own 100% of one LLC and that LLC owns 50% of a partnership LLC, the partnership would file a form 1065 which would generate a K-1 which you would enter on your personal return.  Since you are a single member LLC the K-1 should be issued in your name, not that of the LLC. 

When the lots are sold by the partnership, the sale along with expenses, will be reported on the 1065 which will generate a k-1 for each partner. The K-1 will report each partners share of the gain or loss. The K-1 will then go to your personal return on Schedule E. 

Unless you specifically chose to be treated as an S-Corp, you are considered a disregarded entity. This means for tax purposes you and the LLC are the same thing. You will enter the K-1 in the investment income section of your personal return not in the business section. If your 100% owned LLC does not have any other income, you will not file a Schedule C at all, only a Schedule E.

For any other income you have from your 100% owned LLC, you will still enter it on your Schedule C.  

If you did made the election to specifically be treated as an S Corp, then your LLC would need to file a 1120S.  On the 1120S you would enter the K-1 from the partnership.  Then the S Corp would issue a K-1 to you personally which would include the income from the partnership. You would then enter the K-1 on your personal return.