The compound shown is 1-chloro-2-methylcyclopropane (no configuration specified). Consider only the cyclic (ring-containing) isomers of its molecular formula $\mathrm{C}{}_4\mathrm{H}{}_7\mathrm{Cl}$, with rings treated as planar. Which statements are correct?

Cyclic constitutional isomers of $\mathrm{C}{}_4\mathrm{H}{}_7\mathrm{Cl}$: chlorocyclobutane, 1-chloro-1-methylcyclopropane, 1-chloro-2-methylcyclopropane and (chloromethyl)cyclopropane: 4. Only 1-chloro-2-methylcyclopropane has stereocentres; its two centres carry different groups (Cl versus $\mathrm{CH}{}_3$), so both cis and trans are chiral and there are $2^2=4$ stereoisomers with no meso form. Chlorocyclobutane has a mirror plane through C1 and C3 and is achiral. Total cyclic isomers = 1 + 1 + 4 + 1 = 7.