Whiles it remained (menon). Present active participle of mend, unsold, Peter means.
After it was sold (prathen). First aorist passive of pipraskō, to sell.
How is that thou hast conceived (Ti hoti ethou). Quid esto quod. See note on Luk 2:49. See also Act 5:9. Second aorist middle indicative second person singular of tithēmi. The devil filled his heart (Act 5:3), but all the same Ananias did it too and is wholly responsible.