After one $\alpha$ and two $\beta$ emissions,what happens to the nucleus?

In the given reaction ${}_{Z}^{A}X \to {}_{Z+1}^{A}Y \to {}_{Z-1}^{A-4}K \to {}_{Z-1}^{A-4}K$,the radioactive radiations emitted in the sequence are:

Two radioactive substances $A$ and $B$ of mass numbers $200$ and $212$ respectively, show spontaneous $\alpha$-decay with the same $Q$ value of $1 \text{ MeV}$. The ratio of energies of $\alpha$-rays produced by $A$ and $B$ is . . . . . . .

Explain the basic nuclear process by equation in $\beta$-decay.

Consider a $\beta$ decay reaction:
${}_1^3H \to {}_2^3He + {e^{ - 1}} + \bar v$
The atomic masses of ${}_1^3H$ and ${}_2^3He$ are $3.016050 \, u$ and $3.016030 \, u$,respectively. Find the maximum possible energy of the electron in $MeV$.

$U^{238}$ decays into $Th^{234}$ by the emission of an $\alpha$-particle. There follows a chain of further radioactive decays,either by $\alpha$-decay or by $\beta$-decay. Eventually,a stable nuclide is reached,and after that,no further radioactive decay is possible. Which of the following stable nuclides is the end product of the $U^{238}$ radioactive decay chain?