ormal? I live in Chicago - we brought the Lemon tree indoors when the temp was at 40f.
Citrus blossoms can be touchy. A draft, cooler temps, low light, a change in moisture, can all cause fruit blossoms to drop. Is your plant receiving up to 8 hours of sun a day? Site it near a south or southwest window. You can add a full spectrum grow light if you need to. Some people just want to get it through the winter so they can move it back outdoors.
Lemons normally bloom in spring and fruit matures by fall, but some will flower off and on all year. Here are some care tips that you can compare with yours:
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-blossom-drop.htm
The smaller newer leaves on other branches look very healthy. Will the lost leaves grow back?
No, unfortunately. Leaves do not grow back. Usually, they are replaced by clusters of leaves or branches, though.
Still, you will need to figure out what caused the leaf drop, or you will continue to experience the issue. Typically, this is caused by too much water, wet soils, lack of light, or dry air.
This article will help you to grow citrus indoors:
https://www.gardeningknowhow.com/edible/fruits/citrus/growing-citrus-trees-indoors.htm
Just cut diseased branches
Has that radiator been on? It could cause leaf drop. Also, give it as much light as possible. I suggest removing the sheer curtain and keeping the blinds open or up during the day.
Here are more causes:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaf-drop.htm
https://www.gardeningknowhow.com/edible/fruits/citrus/leaves-falling-off-citrus-tree.htm
Can I grow a Dwarf Lemon tree and Bay Leaf tree in a 1mt x 50 size trough?
Growing a dwarf lemon tree and a bay leaf tree in a 1-meter by 50-centimeter trough is possible, but a larger container may be advisable for long-term root development. Ensure good drainage, use a well-draining potting mix for each tree, and monitor soil moisture. Place the trough in a sunny location, protect from harsh weather, and consider hand-pollinating lemon tree flowers for fruit production. Regular pruning, balanced fertilizer application, and adaptation to local climate conditions contribute to successful container gardening. Be prepared to transplant to larger containers as the trees mature, or do some root pruning. This will mean trimming off about 1/3 of the root ball, and placing it back into its spot.
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm
https://www.gardeningknowhow.com/edible/herbs/bay/container-grown-bay-trees.htm
In the island of Crete
Be sure to get a dwarf, grafted tree if you want fruit. Full sun is important, too. Crete is in zone 10 (unless in mountains) so you can grow it outside on a patio. You can grow it indoors, too, if you provide enough light. Here is more:
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-meyer-lemons.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm