Incorrect statement regarding base catalysed aldol condensation is/are

When acetaldehyde is at fairly high concentration, slow step is formation of the carbanion(enolate)

When acetaldehyde is at low concentration, slow step is nucleophilic attack of carbanion at carbonyl carbon

In case of acetone at any concentration of it, formation of carbanion is slow step

Base catalysed dehydration of aldols follows ${\mathrm{E}}_{1\mathrm{CB}}$ mechanism