Regarding lend-lease, I do not think that it is explicitely stated in the v3 Rules, but some of the wording suggests that multiple lend-lease can be performed in the same turn, provided that it goes to eligible nations, according to each National Reference Sheet.
Specifically, Rule 7.9 mentions: “Major Powers may send lend-lease to other Major and Minor Powers. This can be either military units or IPPs.”
It also mentions in the “Production” subsection that you “Purchase the unit during the Production Phase and place in on the Production Chart with the receiving nations roundel underneath it.”
Finally, rule 11.4 mentions in the “Over Land Zones Delivery Process” that “The lend-lease stops in the first land zone in the receiving nations Home Country”.
The use of plural in all these rules suggests that there may be more than one receiving nation at a time.