Yes.You can special summon more then once in one turn.
Chat with our AI personalities
You have five monster slots on your Field, so even a card that can summon an unspecified amount of monsters (like Return from the Different Dimension) you will still only be able to summon a maximum of 5 to your own side of the field. There are no cards that can increase this, and Trap Monsters take up a monster card slot so it's not like you could have five regular monsters and an Embodiment of Apophis.
No, your opponent cannot Normal or Special Summon any more monsters. They can, however, Tribute Summon monsters if they will end up having fewer or an equal amount of monsters as you. In this scenario, your opponent couldn't Tribute Summon a Level 5 or 6 monster because they would still have one more monster than you. But he/ she can tributed both monsters for a Level 7 or higher monster since they would end up with one monster. The same rule applies to tributes for a Special Summon for cards like "Destiny Hero - Plasma", "Voltanis the Adjudicator", Destiny Hero - Dogma", and more.
If a card looks for a specific number, it will say so, ie, it will specifically say "one" monster. In this case, the opponent has 'a monster', if he has one, two, or even five monsters on the field. So just as long as they've got one or more, and you have none, then you can special summon Cyber Dragon.
Generally, you can only Normal Summon once per turn. However, there are some cards, such as Ultimate Offering and Double Summon that allow you to Normal Summon multiple times.Special Summoning has no limit besides the 5-card Monster Card Zone input. You can Special Summon as many cards as possible in a single turn unless another card specifically prohibits such actions such as Summon Limit.Ultimate OfferingTRAP/Continuous TrapAt the cost of 500 Life Points per monster, a player is allowed an extra Normal Summon or Set.Double SummonSPELL/Normal SpellYou can Normal Summon 1 additional time this turn. You can only gain this effect once per turn.Summon LimitTRAP/Continuous TrapNeither player can Summon more than two times per turn.
The stars are the monster's Level. If you want to Normal Summon a monster of Lv5 or 6, then you must Tribute Summon it by tributing a monster from your side of the field. If the monster is Lv7 or more, you must tribute two monsters. Levels have little effect in-game, they only have an effect when another effect specifically looks at them. So Burden of the Mighty looks at a monster's level to determine how much ATK loss it suffers. The most important thing Level does is how it works with Synchro Summoning. To Synchro Summon a monster, generally you must send a Tuner, and one or more non-Tuners (some rare cases allow more than one Tuner, others require specific components) with combined level equal to the level of the Synchro Monster. So Lv8 Stardust Dragon could be summoned using Lv2 Krebons + Lv6 Destiny Hero Malicious.