Why does Butyne has two isomers? Is there any other structural isomer of Butyne?

Name the following compound:

${\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}$

Name the following compound:

Name the following compound:

${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{OH}$

Name the following compound:

Name the following compound:

${\mathrm{CH}}_3\mathrm{CHO}$

Name the following compound:

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{COOH}$