There's no such thing as a free and necessary lunch

In keeping with his distinction between "world" (mathematical) and "nature" (dynamic) (465-466), Kant calls the first two conflicts of the antithetic of pure reason (the finitude or infinitude of the world with regard to space and time and the existence of simple parts) "world-concepts in a narrower sense" (466), dealing with the composition and divisions of the world. The last two are "transcendent concepts of nature" (467).
The third conflict is over freedom: whether, in addition to the laws of nature, freedom causes certain appearances of the world, or it is simply the laws of nature that do so. According to the former position (the thesis), if there were no freedom (i.e., if there were no unconditioned causes), but only caused causes (i.e., the laws of nature), then there could be no beginning of things and the chain of causality would extend infinitely into the past. This, for Kant, is unacceptable, for "nothing happens without a cause sufficiently determined a priori" (484). The antithesis asserts that freedom leaves causation in an invalid in-between place, violating the law of causality (485).
It seems that tension might exist between freedom and necessity, both of which Kant attributes to the unconditioned (A419/B447). So, under this conception, the unconditioned is both free (i.e., without cause by anything else and the absolute beginning of a series of events) and necessary. But that which must occur (the necessary) seems to be conditioned by that necessity; it occurs because it cannot not occur. This contradicts with the free, which has no condition, no prior cause. How can Kant call the unconditioned both free and necessary What is the relationship between freedom and necessity?
The fourth conflict is concerned with the existence of a necessary being. It is interesting to note the connection between the thesis here (there exists a necessary being) and the thesis of the third conflict (freedom causes certain things). Kant writes that that which is conditioned "presupposes, in respect of its existence, a complete series of conditions up to the unconditioned,,," (A452/B480). This idea assumes that unconditioned causes indeed exist, which the thesis of the third conflict asserts and the antithesis denies. It is necessary to consider these four conflicts not only individually but also collectively.