BJT: what are differences between \$r_{be}\$ and \$r_e\$; \$r_{in}\$ and \$r_{in(t)}\$?
\$r_{be}\$ stands for the resistance located in the path of Base to Emitter (and reverse, it's bidirectional) which is actually placed in Base side and needs to be multiplied to \$\beta\$ if you want to move it to Emitter. It's also known as \$r_{\pi}\$.

\$r_{e}\$ stands for the total resistance seen from Emitter of a transistor, in approximate:

\$r_{e} = \beta r_{\pi} || r_{o} \approx \beta r_{\pi}\$ 

\$r_{o}\$ is the resistance between Emitter and Collector of a BJT which is infinite as usual in approximations.



In high frequencies, some capactive behaviors will be appeared in BJT Transistors. \$r_{in}\$ stands for the input resistance seen usually from Base and it gets time variant if capacitors appear in transistor model, so you'll have a time-dependent resistance in high frequencies notationed as \$r_{in}(t)\$. It's related to advanced topics of BJT transistors.